I believe breeders start counting from the first sign of buds. I bought NL#5 and it was said to finish in 8 weeks, but it took almost 11 to finish. However, it took 3 weeks for buds to show after i flipped. This has happened on every seed grow ive done.
I think it may be different if growing from clone. I just did White russian and its said to finish in 9, which it did counting right from flip.
So if i grow from seed I count from first day of flip so i can compare finish time between strains.